Earphone sound level limiters

The BBC, which has a large and constantly changing variety of equipment fitted with earphone sockets, decided long ago that they would control earphone sound levels by using limiters, and set to work to design some.
Limiters based on the BBC designs are supplied by Canford Audio Ltd. There are three designs, each catering for a range of earphone sensitivities and impedances. The limiters fit in small plastic boxes which are connected in line in the headphone leads.
As an alternative, Canford have modified the design to fit inside the ear piece of the headphone, making a stronger and more tamper proof system. Several types of headphone are available with integral limiters.